1. Field of the Invention
This invention relates to vehicle wheel differentials and, in particular, to a differential lock assembly, or shift mechanism, for the differential.
2. Disclosure of Related Art
Wheel differentials are provided on vehicles to enable a pair of wheels on a common rotational axis to rotate at different speeds while the vehicle is turning. Under certain conditions (e.g., when one of the wheels is traveling over wet or icy pavement while the other wheel is on dry pavement), however, it is desirable to ensure that the differential is locked and that the wheels rotate at the same speed even while turning to ensure increased traction. Accordingly, conventional differentials generally include a differential lock assembly to selectively lock the differential and thereby prevent wheels disposed about a common rotational axis from rotating at different speeds.
A conventional differential includes a differential housing and a differential cage supported thereon by two sets of bearings. The differential further includes a clutch assembly having fixed and sliding clutch members. The fixed clutch member is fixedly coupled to one portion of the differential cage. The sliding clutch member is coupled for rotation with one of two axle half shafts extending from the differential cage. A differential lock assembly is used to selectively shift the sliding clutch member into engagement with the fixed clutch member to thereby prevent relative rotation between the axle half shaft and the differential cage and thereby prevent the wheels supported on the two axle half shafts extending from the cage from rotating at different speeds.
Conventional differentials suffer from several disadvantages due to the location and configuration of the differential lock assembly. First, the size and location of the differential lock assembly often interferes with the placement and/or operation of vehicle suspension components. Second, the lock assembly components are often relatively large in size thereby increasing material, inventory, and tooling costs. Further, the lock assembly components are often difficult to modify without requiring a relatively large number of additional modifications to other components of the differential. Finally, the relatively complex configuration of conventional lock assemblies makes assembly relatively difficult thereby increasing the assembly time and cost.
There is thus a need for an improved wheel differential that will minimize or eliminate one or more of the above-mentioned deficiencies.
The present invention provides a wheel differential having an improved differential lock assembly.
A wheel differential in accordance with the present invention includes a differential housing and a differential cage rotatably supported on the differential housing by a set of bearings. The differential also includes a clutch assembly having a first member fixed to the differential cage and a second member configured to receive an axle half shaft extending from the differential cage for rotation with the axle half shaft. Finally, the differential includes a differential lock assembly. The lock assembly includes a shift chamber that is supported on an outer race member of the set of bearings. The shift chamber may be formed within a bearing cap that is coupled to the differential housing and disposed about at least a portion of the bearing set. The lock assembly further includes a piston disposed within the shift chamber and a pushrod coupled to the piston. A shift arm is also coupled to the pushrod and is configured to engage the second member of the clutch assembly. The piston may be urged in a first direction and a second direction, opposite the first direction, within the shift chamber by the application of biasing or fluid forces. In one embodiment, a spring biases the piston in a first direction while a pneumatic force selectively urges the piston in a second direction against the force of the spring. In another embodiment, pneumatic forces are used to urge the piston in both the first and second directions.
A differential in accordance with the present invention represents a significant improvement as compared to conventional wheel differentials. First, placement of the lock assembly shift chamber on the outer race member of the bearing set moves the components of the lock assembly substantially within the differential housing. As a result, the lock assembly does not interfere with the placement and/or operation of vehicle suspension components. Placement of the lock assembly shift chamber on the outer race member of the bearing set also reduces the size of, and material required for, the differential cage and shift yokexe2x80x94among other components of the differential. This reduction in size and in material requirements reduces inventory, tooling, and manufacturing costs. Second, integration of the shift chamber into the bearing cap results in the additional advantage that modifications to the lock assembly can be made without extensive modifications to other differential components. Third, the less complex design of the inventive differential makes assembly of the differential easier thereby reducing assembly time and capital equipment needs.
These and other features and objects of this invention will become apparent to one skilled in the art from the following detailed description and the accompanying drawings illustrating features of this invention by way of example.